Copolyamides containing caprolactam, lauriclactam and hexamethylene diamine adipate

ABSTRACT

The invention relates to copolyamides containing caprolactam, lauriclactam, hexamethylene diamine adipate and hexamethylene diamine salt of an aliphatic dicarboxylic acid with a carbon chain of 9, 10, 12 or 13 carbon atoms. The copolyamides are useful as heat-sealing agents.

This application is a continuation-in-part of our application Ser. No.384,370 filed July 31, 1973, now U.S. Pat. No. 3,883,485 granted May 13,1975.

This invention relates to copolyamides containing caprolactam,lauriclactam and hexamethylene diamine adipate together with otherpolyamide-forming components as basic units, to a process for producingthese copolyamides and to their use for heat-sealing.

BACKGROUND OF THE INVENTION

It is known that copolyamides containing from 80 to 20% by weight of thebasic unit lauriclactam and, accordingly, 20 to 80% by weight of thebasic units of one or more other polyamide-forming substances, can beused for the production of shaped articles of high bond strength atelevated temperature which are suitable for heat-sealing (DAS1,253,449). It is particularly preferred to use for this purposecopolyamides of lauriclactam and, preferably, caprolactam and/orhexamethylene diamine adipate or hexamethylene diamine sebacate.Theseknown copolyamides into which two or three polyamide-forming monomersare incorporated by condensation as basic units, are widely used in thegarment industry for heat-sealing textiles, especially woven fabrics.Unfortunately, the copolyamides described in DAS 1,253,449 have arelatively high melting point which is above about 110°C, with theresult that they cannot be used for heat-sealing temperature-sensitivesubstrates such as leather, temperarture-sensitive natural and/orsynthetic woven fabrics, non-woven fabrics, felts, tufted fabrics andthe like. Substances with melting temperatures of below about 115°C, ifpossible below 110°C or even below 105°C, are required for heat-sealingtemperature-sensitive substrates of this kind.

SUMMARY OF THE INVENTION

The object of the invention is to find substances which are suitable forheat-sealing temperature-sensitive substrates, show a high bond strengthat low sealing temperatures and after cooling and which nevertheless arehighly resistant to chemical cleaning agents.

The present invention relates to copolyamides containing caprolactam,lauriclactam and hexamethylene diamine adipate as basic units,distinguished by the fact that they contain as and additional basic unita hexamethylene diamine salt of an aliphatic dicarboxylic acidcorresponding to the formula

    HOOC--(CH.sub.2).sub.n --COOH                              (I)

in which n is the number 7, 8, 10 or 11, the basic units beingincorporated into the copolymer in the following proportions:

    caprolactam          25-35% by weight                                         lauriclactam         20-40% by weight                                         hexamethylene diamine adipate                                                                       8-25% by weight                                         hexamethylene diamine salt of                                                 the acid of formula (I)                                                                            10-40% by weight                                     

The invention also relates to a process for the production ofcopolyamides containing caprolactam, lauriclactam and hexamethylenediamine adipate as basic units which is distinguished by the fact thatthe aforementioned basic units and, as an additional basic unit, ahexamethylene diamine salt of an aliphatic dicarboxylic acidcorresponding to formula (I) are polymerised under pressure at elevatedtemperatures by methods known per se.

The copolyamides defined above are used for heat-sealing. Thecopolyamides according to the invention surprisingly show a very lowmelting point of below 110°C, extremely high bond strength at elevatedtemperature, so that they can be used with advantage for heat-sealingtemperature-sensitive substrates, and a high resistance to chemicalcleaning agents.

Copolyamides of the kind whose basic units are incorporated into thecopolyamide by polymerisation in the following proportions are preferredfor the purposes of the invention:

    caprolactam          30% by weight                                            lauriclactam         30-35% by weight                                         hexamethylene diamine                                                         adipate              10-15% by weight                                         hexamethylene diamine                                                         salt of the acid of                                                           formula (I)          15-35% by weight                                     

It is particularly preferred for the copolyamide to contain thehexamethylene diamine salt of the dicarboxylic acid of formula (I) in aquantity of from 20 to 30% by weight.

The acids of general formula (I) have the following names:

n = 7 azelaic acid

n = 8 sebacic acid

n = 10 dodecane dicarboxylic acid

n = 11 brassyli acid

The acids of formula (I) in which n stands for the number 7, 8 or 10 areparticularly preferred for the purposes of the invention, acids in whichn is 7 to 8 being particularly preferred because they are readilyavailable commercial products and lead to copolyamides which can be usedwith particular advantage for heat-sealing.

According to the invention, the copolyamides are produced by methodsknown per se. As in the production of C12-polyamide from lauriclactam,temperatures of from about 280° to 300°C, preferably, a temperature ofabout 290°C, and pressures of from about 10 to 50 atms, preferably fromabout 15 to 30 atms, are generally used. Polymerisation is continued forseveral hours under these conditions. Polymerisation is preferablyfollowed by after condensation for a few hours, preferably for about 1to 3 hours, at a temperature of 250° to 300°C. The catalysts, chainterminators and/or other additives and the process conditions normallyused for the polymerisation of lauriclactam are employed. The process isbest carried out in the absence of air, i.e. in an inert gas atmosphere.The copolyamides according to the invention are preferably used forheat-sealing in the form of fine powders which are applied to thesubstrates to be bonded. A preferred viscosity for the copolyamide whenit is used for the production of films is from about 1.4 to 1.5. Thisfigure denotes the solution viscosity of a 0.5% solution of thecopolyamide in m-cresol at 25°C.

The copolyamides used in accordance with the invention can contain otheradditives, for example dyes, in the usual way.

The copolyamides used in accordance with the invention are copolymerswhich are formed during the polymerisation of a mixture of the polyamideformers. The basic units are condensed into the polymer chain instatistical distribution. The surprising effects described are notobtained when the polyamide formers are polymerised separately from themono polyamides and subsequently melted together with them. Thecopolyamides according to the invention can also have small quantitiesof other polyamide formers condensed into them. However, for reasons ofready accessibility and satisfactory reproducibility of production toform copolyamides with uniform properties, it is generally not advisableto add further polyamide formers.

It is possible by means of the copolyamides according to the inventionto bond substrates of many different kinds with particular advantagetemperature-resistant substrates, to substrates of the same or differenttype. A copolyamide according to the invention is preferably introducedin the form of a powder between the surfaces to be bonded. Thecopolyamide can of course also be used in the form of films, filamentsand chopped filaments. The substrates are then pressed with thepolyamide according to the invention at elevated temperature. Thepressing temperature is governed primarily by the temperaturesensitivity of the substrate. Since the copolyamides according to theinvention develop outstanding bond strength even at very low sealingtemperatures of, for example, from about 100° C or up to 150°C,depending upon their melting range, it is possible to apply extremelylow sealing temperatures. Cooling to room temperature is accompanied byhardening so that the bonded substrates are firmly united. There is noneed for drying or evaporation of solvents.

The copolyamides according to the invention in the form of powders canbe applied to a substrate to be bonded, for example by the powdercoating machines normally used in the coating industry. In thisconnection, it is also possible to coat only selected areas of thesubstrate surface with the copolyamide powder according to theinvention. Examples of substrates to be bonded include textiles ofnatural materials and/or synthetic materials such as wool, silk, cottonand polyesters, polyamides and the like. Other temperature-sensitivesubstrates such as leather, plastics films and the like, can also beheat sealed using the copolyamides according to the invention.

The copolyamides of the invention can be mixed with plasticizers beforebeing used. Suitable plasticizers are, e.g., sulfonic acid derivativesof the following formula ##SPC1##

wherein R₁ stands for hydrogen or methyl, and R₂ for hydrogen, a loweralkyl group, or a cyclohexyl group.

Particularly preferred are benzene- or toluene-sulfonic acid ethylamide. Corresponding commercial products can be obtained. Suchcommercial products are, e.g., mixtures of p- and o-toluene sulfonicacid alkyl amides. Phenol carboxylic acid or alkyl esters thereof mayalso be employed as placticizers. Examples thereof are butyl-p-hydroxybenzoate, lauryl-p-hydroxy-benzoate, p-oxy- benzoic acid,octyl-p-oxybenzoate. Bisphenol A and similar compounds may also beemployed as placticizers. Of course, it is necessary to use in each caseplasticizers which are compatible with, or suitable for, the particularcopolyamides employed, as is well understood by persons skilled in theart. The plasticizers can be worked into the copolyamides by mixing themwith the latter and heating the mixture at temperatures above themelting point. At these temperatures they can, e.g., be extruded, inorder to serve for the manufacture of threads, foils, and the like.Powders can also be produced.

When the copolyamides are employed in powder form, it is sometimessuitable to disperse these copolyamide powders in aqueous dispersions,to apply such dispersions, e.g., to textile parts to be joined,especially materials inserted in clothing, e.g., by point coating, thento dry the textiles thus coated, to sinter them, to fix them, and toheat-seal them to the materials to be joined, e.g., by ironing thetextiles with a flatiron or with an ironing press (cf., e.g. GermanPats. No. 2,007,971 and No. 2,229,308). The dispersions usually containthickeners and stabilizers in order to produce stable dispersions. Suchthickeners and stabilizers are well known to the artisan, e.g.,polymeric organic acids, longchain fatty acids, and the like. It ispractical to make the dispersions slightly alkaline. When suchdispersions are used, it is particularly preferred not to mix theplasticizers with the copolyamides, as described above, but to add theplasticizers as a further component to the dispersions.

The quantity of plasticizers may amount up to about 50% by weight of thetotal quantity of copolyamide and plasticizer. Particularly preferred isan amount of plasticizer up to about 25% by weight with relation to thetotal quantity of copolyamide and plasticizer.

It has already been pointed out above that the copolyamides of theinvention may also contain a dyestuff or other customary additives.Thus, the copolyamides may contain, e.g., customary antioxidants,anti-inflammable agents, and particularly optical brighteners as well asfluorescence-causing agents. A wide variety of such agents, which can beobtained as commercial products, are known in the art. Of course, onlyadditives which are resistant to the heat-sealing temperatures appliedcan be employed.

DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1

350 parts by weight of caprolactam, 150 parts by weight of adipic acidhexamethylene diamine salt, 350 parts by weight of lauriclactam, 150parts by weight of azelaic acid hexamethylene diamine salt (6,9-salt),12 parts by weight of adipic acid as polymerisation-degree regulator and100 parts by weight of distilled water, are weighed into an autoclaveequipped with stirring mechanism. The atmospheric oxygen inside theautoclave is removed by repeated rinsing under pressure with purenitrogen. The reaction mixture is heated to 290°C and the pressureinside the autoclave limited to 25-30 atms by suitably adjusting thevalve. The reaction mixture is exposed to the aforementioned pressureand temperature conditions for a period of 3 hours during which it isstirred. The pressure is then reduced to normal pressure over a periodof 2 hours. The reaction mass is then aftercondensed while stirring for2 hours in the absence of pressure under a gentle stream of nitrogen.

On completion of the pressure free after-condensation phase, thetemperature is reduced to 180°-200°C and the melt spun through a nozzlein the form of a monofil by means of a gear pump, cooled and granulated.

The resulting granulates have a melting range of 95° to 102°C, asmeasured on a KOFLER heating-stage microscope, and a relative solutionviscosity of 1.45, as measured in 0.5% solution in m-cresol at 25°C bymeans of an Ostwald viscosimeter.

The azelaic acid hexamethylene diamine salt used in this Example wasprepared as follows from a commercial-grade azelaic acid known as EMEROX1144;

1 mol (190.0 g) of EMEROX 1144 are dissolved under reflux inisopropanol, followed by the addition while stirring of 1.02 mol (118.5g) of hexamethylene diamine, also dissolved in isopropanol. The whitedeposit formed is filtered off and dried. The resulting azelaic acidhexamethylene diamine salt (6,9-salt) melts at 150° to 152°C and has apH-value of 7.6, as measured in a 1% aqueous solution.

EXAMPLE 2

300 parts by weight of caprolactam, 100 parts by weight of AH-salt, 300parts by weight of lauriclactam, 300 parts by weight of azelaic acidhexamethylene diamine salt, 12 parts by weight of adipic acid aspolymerisation-degree regulator and 100 parts by weight of distilledwater, are reacted under the polycondensation conditions described inExample 1.

The product is a copolyamide melting at 90° to 95°C, as measured on aKOFLER heating-stage microscope.

EXAMPLE 3

A copolyamide at 85° to 90°C is prepared from the following componentsin the manner described in Example 1: 300 parts by weight ofcaprolactam, 150 parts by weight of AH-salt, 400 parts by weight oflauriclactam, 150 parts by weight of sebacic acid hexamethylene diaminesalt (6,10-salt) and 12 parts by weight of adipic acid.

EXAMPLE 4

300 parts by weight of caprolactam, 150 parts by weight of AH-salt, 400parts by weight of lauriclactam, 150 parts by weight of dodecanedicarboxylic acid hexamethylene diamine salt (6,12salt), 12 parts byweight of adipic acid and 100 parts by weight of distilled water, arereacted under the polycondensation conditions described in Example 1.

A copolyamide melting at 95° to 102°C is obtained.

The 6,12salt used is prepared from the commercially available componentsdescribed in Example 1.

EXAMPLE 5

A copolyamide melting at 100° to 110°C is prepared from the followingcomponents under the polycondensation conditions described in Example 1:300 parts by weight of caprolactam, 150 parts by weight of AH-salt 350parts by weight of lauriclactam, 135.5 parts by weight of brassylic acid(C₁₃ -dicarboxylic acid), 64.5 parts by weight of hexamethylene diamine,12 parts by weight of adipic acid.

EXAMPLES 6 to 15

Copolyamides were prepared from the starting components specified inTable 1 below in accordance with the procedure described in Example 1.The following abbreviations were used:

6 = caprolactam

12 = lauriclactam

6,6= AH-salt

6,9= hexamethylene diamine azelaic acid salt

6,10= hexamethylene diamine sebacic acid salt

6,12= hexamethylene diamine dodecane dicarboxylic acid salt

6,13= hexamethylene diamine brassylic acid salt

The melting temperatures of the copolyamides obtained are also shown inTable 1.

In the individual Examples, the quantities in which the basic units areused can generally be changed by about ± 3% or at least by 1.5% withoutadversely affecting the properties of the copolyamides obtained to anyappreciable extent.

                  Table 1                                                         ______________________________________                                        Example                                                                              Monomer composition                                                    %        %     %     %   %    %    %    Melting range                         6        12    6,6   6,9 6,10 6,12 6,13 °C                             ______________________________________                                        6      25    35    20  20  --   --   --   95 - 100                            7      30    20    20  30  --   --   --   98 - 106                            8      30    30    20  20  --   --   --   95 - 100                            2      30    30    10  30  --   --   --   92 -  98                            9      30    35    15  20  --   --   --   90 - 100                            10     30    40    15  15  --   --   --   90 -  95                            11     30    40    10  20  --   --   --   101 - 107                           1      35    35    15  15  --   --   --   95 - 102                            12     30    35    15  --  20   --   --   83 -  91                            13     30    30    10  --  30   --   --   91 -  99                            3      30    40    15  --  15   --   --   84 -  90                            14     30    30    10  --  --   30   --   95 - 103                            15     30    35    15  --  --   20   --   96 - 103                            4      30    40    15  --  --   15   --   95 - 102                            5      30    35    15  --  --   --   20   100 - 110                           ______________________________________                                    

COMPARISON TEST

In this comparison test, the bond strength of a copolyamide according tothe invention is compared with that of a copolyamide containing only thebasic units caprolactam, lauriclactam and AH-salt.

The copolyamide of Example 13 which has a melt viscosity of 3000 poisesat 140°C, is used as the copolyamide according to the invention.

A copolyamide of the following polyamide-forming basic units is used asthe comparison copolyamide: 30% of caprolactam, 45% of lauriclactam and25% of AH-salt.

This copolyamide has a melting temperature of from -110° to 120°C and amelt viscosity of 2000 poises at 140°C.

The polyamides were each ground while cooling and separated by siftinginto a fraction of 0 to 200 nm.

The two powder fractions were applied to a conventional interliningmaterial in an 11-mesh pattern in a weight of 16 ± 1 g per m² by meansof a powder pointing machine of the kind commonly used in the coatingindustry.

The coated interlinings thus obtained were ironed with apolyester/cotton fabric under a constant pressure of 350°p/cm² on anelectrically heated ironing press of the kind commonly used in thegarment industry, both the plate temperature and the contact time beingvaried.

The declamination strengths of 2.5 cm wide laminate strips were measuredby means of a tension tester.

The declamination strengths (p/2.5 cm) specified in Table 2 weremeasured:

    Contact Plate temperature of the ironing                                      time    press (°C)                                                     (seconds)                                                                     110        120     130     140   150                                          ______________________________________                                                400    700     600   800   900   Invention                             6                                                                                    --     --      100   200   200   Comparison                                   500    900     900   900   1200  Invention                            10                                                                                    --     --      200   300   400   Comparison                                   700    1100    1100  1200  1200  Invention                            15                                                                                    --     --      300   400   700   Comparison                                   700    1200    1000  1100  1600  Invention                            18                                                                                    --     --      350   500   800   Comparison                           ______________________________________                                    

It can be seen from the Table that extremely good adhesion is obtainedeven at very low plate temperatures of the ironing press, i.e. at verylow sealing temperatures of 110° and 120°C, whereas no adhesion isobtained with the conventional copolyamide at sealing temperatures aslow as these. The conventional polyamide only produces firm adhesion athigher sealing temperatures. What is claimed is:

1. A composition of matter comprising a copolyamide consistingessentially of recurring units of caprolactam, lauriclactam,hexamethylene diamine adipate and a hexamethylene diamine salt of analiphatic dicarboxylic acid of the formula

    HOOC--(CH.sub.2).sub.n --COOH                              (I)

in which n is the number 7, 8, 10 or 11, said units being incorporatedin the copolyamide by polymerisation in the following proportions;

    caprolactam          25-35% by weight                                         lauriclactam         20-40% by weight                                         hexamethylene diamine adipate                                                                       8-25% by weight                                         hexamethylene diamine salt of                                                 the acid of formula (I)                                                                            10-40% by weight                                     

and a plasticizer which is compatible with and suitable for plasticizingsaid copolyamide.
 2. The composition according to claim 1, wherein theunits are incorporated in the copolyamide by polymerisation in thefollowing proportions.

    caprolactam          about 30% by weight                                      lauriclactam         30-35% by weight                                         hexamethylene diamine adipate                                                                      10-15% by weight                                         hexamethylene diamine salt of                                                 the acid of formula (I)                                                                            15-35% by weight.                                    


3. The composition according to claim 1, wherein the hexamethylenediamine salt of the dicarboxylic acid of formula (I) is incorporated inthe copolyamide in a quantity of from 20 to 30% by weight.
 4. Thecomposition according to claim 1, in which n in formula (I) is 7, 8 or10.
 5. The composition according to claim 4, wherein n in formula (I)stands for the number 7 or
 8. 6. A process for the production of a heatbonding composition comprising the steps of polymerizing caprolactam,lauriclactam, hexamethylene diamine adipate and a hexamethylene diaminesalt of an aliphatic dicarboxylic acid corresponding to the formula

    HOOC--(CH.sub.2).sub.n --COOH

(i) in which n is 7, 8, 10, or 11, under pressure at elevatedtemperature in the following quantitative proportions:

    caprolactam          25-35% by weight                                         lauriclactam         20-40% by weight                                         hexamethylene diamine adipate                                                                       8-25% by weight                                         hexamethylene diamine salt of                                                 the acid of formula (I)                                                                            10-40% by weight                                     

thereby forming a copolyamide, and incorporating a plasticizer into saidcopolyamide which is compatible with and suitable for plasticizing saidcopolyamide.
 7. A process according to claim 6, in which the units arepolymerised in the following quantitative proportions:

    caprolactam          about 30% by weight                                      lauriclactam         30-35% by weight                                         hexamethylene diamine adipate                                                                      10-15% by weight                                         hexamethylene diamine salt of                                                 the acid of formula (I)                                                                            15-35% by weight.                                    


8. A process according to claim 6, wherein the hexamethylene diaminesalt of the dicarboxylic acid of formula (I) is incorporated in thecopolymer in a quantity of from 20 to 30% by weight.
 9. A processaccording to claim 6 wherein n in formula (I) is 7, 8 or
 10. 10. Aprocess according to claim 9 wherein n in formula (I) is 7 or
 8. 11. Aprocess according to claim 6 wherein polymerisation is carried out at atemperature of from 280° to 300°C. and under a pressure of 10 to 50atms.
 12. A process according to claim 6 wherein after-condensation iscarried out for 1 to 3 hours under normal pressure at 250° to 300°C. 13.The composition of matter as defined by claim 1, wherein saidplasticizer is present in an amount up to about 50% by weight of thetotal composition.
 14. The composition of matter as defind by claim 13,wherein said plasticizer is present in an amount up to about 25% byweight of the total composition.
 15. The composition of matter asdefined by claim 1, wherein said plasticizer is selected from the groupconsisting of a sulfonic acid derivative of the formula ##SPC2##whereinR₁ is hydrogen or methyl and R₂ is hydrogen, lower alkyl or cyclohexyl;a phenol carboxylic acid; a phenol carboxylic acid alkyl ester andBisphenol A.
 16. The composition of matter as defined by claim 15,wherein said plasticizer is selected from the group consisting ofbenzene sulfonic acid ethyl amide, toluene sulfonic acid ethyl amide,butyl-p-hydroxy benzoate, lauryl-p-hydroxy-benzoate, p-oxy-benzoic acid,octyl-p-oxy benzoate and Bisphenol A.
 17. The composition of matter asdefined by claim 1, further comprising an aqueous dispersant.
 18. Thecomposition of matter as defined by claim 17, further comprising athickener and a stabilizer.